Buggy code:
@ Exception { <START_BUG> final LineFileDocs docs = new LineFileDocs ( random ) ; <END_BUG> final Directory d = newDirectory ( ) ; final RandomIndexWriter w = new RandomIndexWriter ( random , d ) ; final int numDocs = atLeast ( 10 ) ; for ( int docCount = 0 ; docCount < numDocs ; docCount ++ ) { w . addDocument ( docs . nextDoc ( ) ) ; } final IndexReader r = w . getReader ( ) ; w . close ( ) ; final List < BytesRef > terms = new ArrayList < BytesRef > ( ) ; final TermsEnum termsEnum = MultiFields . getTerms ( r , "body" ) . iterator ( null ) ; BytesRef term ; while ( ( term = termsEnum . next ( ) ) != null ) { terms . add ( BytesRef . deepCopyOf ( term ) ) ; } if ( VERBOSE ) { System . out . println ( ( ( "TEST:<seq2seq4repair_space>" + ( terms . size ( ) ) ) + "<seq2seq4repair_space>terms" ) ) ; } int upto = - 1 ; final int iters = atLeast ( 200 ) ; for ( int iter = 0 ; iter < iters ; iter ++ ) { final boolean isEnd ; if ( ( upto != ( - 1 ) ) && ( random . nextBoolean ( ) ) ) { if ( VERBOSE ) { System . out . println ( "TEST:<seq2seq4repair_space>iter<seq2seq4repair_space>next" ) ; } isEnd = ( termsEnum . next ( ) ) == null ; upto ++ ; if ( isEnd ) { if ( VERBOSE ) { System . out . println ( "<seq2seq4repair_space>end" ) ; } assertEquals ( upto , terms . size ( ) ) ; upto = - 1 ; } else { if ( VERBOSE ) { System . out . println ( ( ( ( "<seq2seq4repair_space>got<seq2seq4repair_space>term=" + ( termsEnum . term ( ) . utf8ToString ( ) ) ) + "<seq2seq4repair_space>expected=" ) + ( terms . get ( upto ) . utf8ToString ( ) ) ) ) ; } assertTrue ( ( upto < ( terms . size ( ) ) ) ) ; assertEquals ( terms . get ( upto ) , termsEnum . term ( ) ) ; } } else { final BytesRef target ; final String exists ; if ( random . nextBoolean ( ) ) { if ( random . nextBoolean ( ) ) { target = new BytesRef ( _TestUtil . randomSimpleString ( random ) ) ; } else { target = new BytesRef ( _TestUtil . randomRealisticUnicodeString ( random ) ) ; } exists = "likely<seq2seq4repair_space>not" ; } else { target = terms . get ( random . nextInt ( terms . size ( ) ) ) ; exists = "yes" ; } upto = Collections . binarySearch ( terms , target ) ; if ( random . nextBoolean ( ) ) { if ( VERBOSE ) { System . out . println ( ( ( ( "TEST:<seq2seq4repair_space>iter<seq2seq4repair_space>seekCeil<seq2seq4repair_space>target=" + ( target . utf8ToString ( ) ) ) + "<seq2seq4repair_space>exists=" ) + exists ) ) ; } final TermsEnum . SeekStatus status = termsEnum . seekCeil ( target , random . nextBoolean ( ) ) ; if ( VERBOSE ) { System . out . println ( ( "<seq2seq4repair_space>got<seq2seq4repair_space>" + status ) ) ; } if ( upto < 0 ) { upto = - ( upto + 1 ) ; if ( upto >= ( terms . size ( ) ) ) { assertEquals ( END , status ) ; upto = - 1 ; } else { assertEquals ( NOT_FOUND , status ) ; assertEquals ( terms . get ( upto ) , termsEnum . term ( ) ) ; } } else { assertEquals ( FOUND , status ) ; assertEquals ( terms . get ( upto ) , termsEnum . term ( ) ) ; } } else { if ( VERBOSE ) { System . out . println ( ( ( ( "TEST:<seq2seq4repair_space>iter<seq2seq4repair_space>seekExact<seq2seq4repair_space>target=" + ( target . utf8ToString ( ) ) ) + "<seq2seq4repair_space>exists=" ) + exists ) ) ; } final boolean result = termsEnum . seekExact ( target , false ) ; if ( VERBOSE ) { System . out . println ( ( "<seq2seq4repair_space>got<seq2seq4repair_space>" + result ) ) ; } if ( upto < 0 ) { assertFalse ( result ) ; upto = - 1 ; } else { assertTrue ( result ) ; assertEquals ( target , termsEnum . term ( ) ) ; } } } } r . close ( ) ; d . close ( ) ; } private void addDoc ( RandomIndexWriter w , Collection < String > terms , Map < BytesRef , Integer > termToID , int id ) throws IOException { } private boolean accepts ( CompiledAutomaton c , BytesRef b ) { } public void testIntersectRandom ( ) throws IOException { } private Directory d ; private IndexReader r ; private final String FIELD = "field" ; private IndexReader makeIndex ( String ... terms ) throws Exception { } private void close ( ) throws Exception { } private int docFreq ( IndexReader r , String term ) throws Exception { } public void testEasy ( ) throws Exception { } public void testFloorBlocks ( ) throws Exception { } public void testZeroTerms ( ) throws Exception { } private String getRandomString ( ) { } public void testRandomTerms ( ) throws Exception { } private boolean seekExact ( TermsEnum te , String term ) throws IOException { } private String next ( TermsEnum te ) throws IOException { } private BytesRef getNonExistTerm ( BytesRef [ ] terms ) { } private static class TermAndState { public final BytesRef term ; public final TermState state ; public TermAndState ( BytesRef term , TermState state ) { } } private void testRandomSeeks ( IndexReader r , String ... validTermStrings ) throws IOException { } }

Fix:
final LineFileDocs docs = new LineFileDocs ( random , defaultCodecSupportsDocValues ( ) ) ;